Capacitatively-actuated loud speaker



June 7 1927.

-J. DEPEW 5 CAPACITATIVELY ACTUATED LOUD sPEAKER File@ Feb. 12. 1926 I Patented `lune 7, 1927.

UNITED STATES 1,631,583. PATENT OFFICE.

JOHN DEPEW, F NEW YORK, N. Y., .ASSIGNOR T0 IGNATZ LAUTER, 0F NEW YORK, N. Y.

CAPACITATIVELY-ACTUATED LOD SPEAKER.

Application mega February 12, 192e. 'serial No. 87,974.

`\ My invention relates to ldud speakers of the kind suitable for use with'radio broad' ceivers, and various other relations in which loud sounds are to be produced or controlled from exceedingly small initial variations in the elcctromotive forces or amperage of electric currents.

More particularly stated, I seek to .produce a loud speaker provided with adiaphragm.

of insulating material actuated by the attraction and repulsion of stationary conductors of large capacity which are energized ,f by

electrical charges varying in electromotive force from moment to moment, under control Vof an amplifying device, such as'an' audion tube.

I have made the discover that in the manhragm can be so actuated as to produce considerable disturbance in the air, and thus to throw oi sound waves' resulting in sounds of great volume and fidelity of expression.

Other objects and aims of the invention, more or less specic than those referred to above, will be in part obvious and inpart pointed out in the course of the followingl description of the elements, combinations,

- 3U arrangements of parts and applications of principles, constituting the invention, and the scope of rotection contemplated will be indicated in t e appended claims.

4In the accompanying drawings which are to be taken as a part of this specification,

\ Figure`2 isa section on the line 2-2 of Figure 1 looking in the direction indicated by the arrows. '-1 1 Figure 3 is a section similarto Figure 2,

and in which I have shown merely a preerred form of embodiment of the invention:

Figure 1 is' a view, partly a perspective and partly a diagram, showing one form of 0 my improved loud speaker and suitable electric circuits for use therewith.

but shows a form of my invention in which the mounting of the diaphragm is somewhat i different from thatl appearing in Figure 2.A Figure 4 is a section similar to Figure 2,

A but showing the diaphragm asl mounted in still another manner.

Referring now to the. drawings for describing detail the structure therein shown-z Two plates 5, 6, made of-metal and pro vided with holes 7, serving as acoustical apertures, are disposed parallel with each other and held in.l position by aid of bolts 8 carrylng nuts 9 and sleeves 10 and 11.as indicated more particularly in 'Figure 2. The sleeves l0 and 11 are of insulating material and are so litted together -as to form joints, one of which is shown at 12. Enclrchng the sleeves 10, 11, are metallic washers 14, 15. These washers lit-upon oping a` thickness of not more ythan a thousandth `of an inch.

As hereinafter more particularly set forth, differences of potential are devel p d between the plates 5 and 6 during e peratio`n of my device, and as a consequence there are dierences of potential developed between tlie metallic washers 14 and 15, shown more particularly in Figure 2. The washers 14 and 15 are close together, being separated by only the thickness 'of the diaphragm 13, and insulated from each other by thls diaphragm. Thus each washer 14 and its mat@ mg washer 15 act like the walls of a small condenser. Since the plates 5, 6, act like the Walls of a large condenser and are in metallic contact with the washers 14 and 15 with which they are associated, 'it follows that. there is a considerable capacitative eli'ect upon opposite sides of the `diaphragm 13, and that this eiect is localized to some extent, relatively to the diaphragm, by the metallic Washers 14 and 15.

` In some instances I prefer not to use the metallic washers 14 andv 15, but to employ instead the 'structure shown in Figure- 3.- Here the diaphragmhas the form indicated at 16, and is engaged upon its opposite sides by rubber washers 17 and 18. In. this case the bolt'8 and its nut 9 are insulated from the metallic plates 5 and 6v by means of sleeves 19 and 20 lof insulating material. In

. a grounding switch at 31, and a ground wire 33 extends from thev this Pform of my ,invention the ca'pacitative effect of the conducting members upon opposite sides of the diaphragm 16 is not localized as in the form shown in Figure 2, but On the other hand the distribution of the capacitative effect relatively to the diaphragm 16 is somewhat more uniform.

In the forms of my invention contemplated by Figures 1 to 3 inclusive the diaphragm is/always held firmly, though resiliently, by its margin, and if desired may be under tension.

Where it is desired that the diaphragm be loose and free relatively to the plates 5 and 6 and parts connected therewith, I employ the form shown in Figure 4.' Here the. diaphragm appears at 21, and extending through a hole in it isa washer 22, of insulating material, engaging the plates 5 and 6. Extending through this washer and through the plates 5 and 6 is the bolt 8 and" sleeveslO and 11.

A pair of binding posts 23 and 24, carried by the the plates 5, 6, 'with appropriate electrical circuits.

The plates 5, 6, are provided with feet 25, either made of insulating material or resting upon a surface of insulating material, and serving as supporting members for the loud speaker.

An aerial appears at 26, an audion tube at 27, a B battery at 32. An aerial aerial 26 to the grid 34 of the audion tube 27, and the audion filament is shown at 35 and the audion plate at 36. The filament circuit appears at 37, and the A battery at 38, and included in the filament circuit in the conventional manner.

A wire 39 extends from the plate 36 to the binding post 23. The impedance coil 30 is tapped on to thisy wire, and connects the same with the B battery 28. Connected with the B battery 28 is a wire 40. Connected with this wire isa wire 41, leading to the binding post 24, and also a wire 42 which is connected with the`grounding switch 31 and with a wire 43, the vlater `leading to the filament circuit 37. Whenever it is desired that the filament circuit be grounded the grounding switch 31 viS closed, but if the filament circuit is to be leftungrounded the grounding switch 31'is left open.

Generally' speaking, the action of the aerial 26 and audion tube 27 are the same asl in well known forms of receivers; However, the connections and actions of the B battery 28 are 'diierent The circuit through which a flow of current from the B battery' 28 takes place may be traced as follows: B battery 28, wire 40, wires 42 and 43, a part of flament'circuit 37, filament 35, through vacuum to` plate 36, and thence lates 5 and 6, are used in connecting'` at 28, an impedance at 30,-

diaphragm,

through a part of wire- 39 and .through impedance coil 30 back to B battery 28. It will be notd, however, current from the B battery`can pass through the loud speaker via wires 39 and 40, because the plates5 and 6 are insulated from4 each other, these plates are nevertheless subjected to differences of potential, because they are bridged across the B battery 28. Itwill also be noted that variations in the electromotive force of the B battery inust produce variations in the differences in potential between the plates 5 and 6, andvthat these diderences f in potential are qualiiied by the action of the impedance coil 30, so that theplates 5 and 6 are affected one at a time, as far as practicable, by any given change of potential. In other words, any vari ations in the current of the B battery may be considered as the equivalent of an electrical impulse travelling Afrom the B battery to the plates 5 and 6 respectively, but reaching the plate 6 a trifle earlier than dthe plate 5, owing to the coil 30. It follows as a necessary consequence that the diaphragm 13 is alternately attracted and repelled by each of the plates 5 and 6. Because thus actuated, the diaphragm is moved back and forth with a vibratory motion, and gives off sound waves.

By the use of the metallic washers 14 and 15, above described with reference to Figure 2, and consequently by localization of the capacitative effect exerted upon 'opposite sides of the diaphragm 13, the action of the diaphragm is for mamy purposes greatly improved.

On the other hand, in instances where I use the form of my invention above described with reference' to Figure 3, the diaphragm 16has greater freedom of movement, owingto the resilience of the rubber washers 17 and 18, and for many purposes this increasedfreedom of movement of the and particularly near its outer edges, is preferable to the localized capacitative effect above described.l

In the construction shown in Figure 4 the diaphragm, shown at 21, has still greater freedom, and in some instances this is fully as desirable as the other advantages above that while no direct* l impedance or retardation of the impedance v described with reference to the constructions iaphragm 21 may bein loose contact with` each of the lates and 6. This is upon the principle t at` with the diaphragm thus mounted it has suiiicient freom of movement to perform vibratory'movements of audio frequency sufficient in magnitude to give olf sound of considerable volume.

In the form of my invention shown inv 5 and 6, and especially by placing them ad-v jacent the middle of these plates, the diaphragm is virtually subdivided into a number of smaller diaphragms, and its freedom to respond to the more delicate impulses brought to bear upon it by the condenser plates is greatly improved.

I point out, in addition, that in my device the diaphragm, though made of considerable area, is easily actuated throughout practically its entire area, and that this fact makes for greatl improved elliciency.

While show my invention as adapted for use in connection with an aerial and thus as under control of electromagnetic waves, it will be understood that I may substitute any known equivalent for the aerial, and thus may control my device by means of a telephone line or by anyv other agency capable of energizing an audion or equivalent instruyment 1n the conventional manner.' Thus the particular circuit shown and described is not essentlal.

The principal characteristic of this invention is the use, in connection with one or more condenser plates adapted to be charged to varying degrees of potential, of a diaphragm madeof insulating' materialv and adapted to be attracted and repelled' electrostatically thereby, so as to produce acoustical vibrations. 4

While I have shown and described a par- -ticular means for holding the plates and the .diaphragm in their respective operative p0- sitions nevertheless an other appropriate means may obviously e employed to this en 4 It will also be understood that I claim for my loud speaker all of the uses to which a loud speakercan be applied,and in additionit should benoted that while for the sake of' simplicity I showin each form 'of my invention only a single pair of condenser plates, any number of these plates, arranged in pairs, may be grouped together for the purpose of .increasing the size, strength, or capacity of the device as a whole.

As many changes'could be made in this construction without departing from the scope of the invention as defined in the fol;

lowing claims, it is intended that all matter conta-ined `in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not in a limitin sense.

aving thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. A device of the class described comprising two plates of conducting material spaced apart and insulated from each other, an acoustical diaphragm made of insulating material and located between said plates of conducting material, and means for subjecting said plates of conducting material to varying potentials in vorder to cause said plates to attract and' repel said diaphragm and thus toactuate said diaphragm.

2. A device of the class described'omprising two plates of conducting material spaced apart and insulated from each other-so as to serve as condenser plates, a diaphragm of insulating material disposed between said plates, and electric means connected with sai'l plates and controllable by electric variations for the purpose of causing one of said plates to attract, and the other of said plates f to repel, said diaphragm.

3. Adevice of the class described comprising two plates of conducting material spaced a slight distance apart in substantially parallel relation to each other and insulated rom each other,- means to variably electrically excite said plates, and a diaphragm of insulating material disposed between said plates to be actuated by the electrical variations thereof.

4. A device of the class described comprising two plates of conducting material spaced a slight distance apart in substantially parallel relation to each other and insulated from each other, holding means for said plates, means to variably electrically excite said plates, and a diaphragm of insulating' material disposed between said plates held by said holding means and adapted to be actuated by the electrical variations of said plates. v

5. A device of the class described, comprising a pair of plates of conducting material insulated from each other and serving as condenser plates, a diaphragm of insulating material disposed between said plates and freeto vibrate in response to attractions and repulsions thereof, a source of electricity for charging said plates to varying potentials4 and a circuit bridged across said plates` and connected with said source of electricity, said circuit including an impedance for retarding the action of one of said' plates relatively to the other.

6.' A device of the class described comprising two platesof conducting material-spaced i a a slight distance.v apart inv substantially the diaphragm at various spaced points parallel relation to each other andinsulated throughout the extent of the diaphragm to from each other, means to variably electrithereby hold said spaced points firmly becally excite said plates, a daphragmof intween the two plates for vthe purpose desulating material disposed between said scribed.

plates to be actuated by the electrical Varia-v In testimony whereof I affix my signature. i

tions thereof, and means carriedby said v p \'pla tes projecting therefrom to press against K OHN DEPEW.'v 

